Mixture for the manufacture of antistatic floor coverings and coatings

ABSTRACT

A mixture containing a cold-curing liquid synthetic resin combination, an anti-sedimentation agent and aluminium grit is used for the manufacture of antistatic floor coverings or coatings, which are colorful or lightcolored and have a uniform electrical conductivity of good reproducibility.

This is a continuation of application Ser. No. 473,548, filed on May 28, 1974, now abandoned.

Since the introduction of liquid synthetic resins based on epoxide resins, polyurethanes or unsaturated polyesters, which cure through a polyaddition or polymerisation reaction with suitable curing agents and catalysts at room temperature, these plastics have found increased use, inter alia, in the fields of corrosion protection, in the form of chemically resistant coatings and of jointless hard-wearing floor coverings. In particular the liquid, solvent-free, aromatic epoxide resins, in combination with specially formulated liquid curing agents, for example based on polyamine adducts or polyaminoamide resins, have attained great and ever-increasing importance in practice due to the excellent mechanical properties of the cured coated materials, such as compressive strength, flexural strength, adhesion to various substrates, impact strength, abrasion resistance and chemical resistance, in the fields of use mentioned.

To prevent such coverings acquiring an electrostatic charge, electrically conducting, so-called antistatic, coverings, especially for floors, have been developed in recent years. Such special coverings are considered, above all, for areas where there is a severe explosion hazard, such as, for example, in operating theatres of hospitals, in paint shops, in large garages and in the manufacturing areas of chemical concerns. At the present time, special carbon blacks and graphite are predominantly used as the fillers for achieving the requisite electrical conductivity of such coverings. These floors are not popular, because of the black or dark grey surfaces, and in many cases do not meet the aesthetic requirements of the personnel working in the areas concerned. This limitation on the possible selection of colour shade also prevents the broader use of antistatic floor coverings.

It is also known to manufacture antistatic floor coverings using metal particles, such as aluminium flakes or copper filings. Here, the disadvantage is the non-uniform electrical conductivity, which turns out different from case to case. Admittedly, a process is known, from German Auslegeschrift 1,544,968, according to which this disadvantage is avoided; however, in return it is necessary to accept the fact that prior to the application of the plastic layer containing metal an undercoat of good conductivity, for example containing graphite, must be applied. This undercoat must then be cured and dried before the plastic covering can be applied.

It has now been found that using the mixture according to the invention, antistatic floor coverings and coatings can be manufactured which, on the one hand, are colourful or light-coloured, for example coloured in pastel shades and on the other hand have a uniform electrical conductivity of good reproducibility, and at the same time the application of one or more conducting undercoats is no longer required.

The mixture according to the invention is characterised in that it contains a cold-curing liquid synthetic resin combination, an anti-sedimentation agent and 45-70 percent by weight, based on the mixture, of aluminium grit and, optionally, fillers and/or, preferably, pigments. Preferably, the mixture contains 30-45%, especially 37-40%, of resin combination, 3-30%, especially 18-30%, of pigments and 45-65%, especially 50-60%, of aluminium grit. The particles of the aluminium grit are preferably 0.35-1.2 mm long.

Possible synthetic resin combinations are liquid epoxide resins, preferably based on aromatic compounds, or mixtures of resins based on aromatic compounds, such as bisphenol-A diglycidyl ether, with aliphatic epoxide resins, such as polyglycidyl ethers of polyalcohols, for example pentaerythritol, hexanetriol, butanediol or glycerol, in combination with liquid curing agents for these resins. As such curing agents there may be mentioned aliphatic or cycloaliphatic polyamines or their liquid adducts, containing at least one primary amino group, with polyepoxides, and also liquid polyaminoamide resins, that is to say reaction products of fatty acids and polyamines.

Further suitable synthetic resin combinations are those based on polyurethanes, such as, for example, a mixture of liquid polyester resins or polyether resins having a hydroxyl number of between 1.7 and 12% and liquid polyisocyanates, preferably based on diphenylmethane-4,4'-diisocyanate, as the curing agent.

Further suitable synthetic resin combinations are binders based on liquid unsaturated polyester resins, unsaturated monomeric compounds which react therewith, such as, for example, styrene, vinyltoluene or acrylic acid esters, and a peroxide catalyst.

Finally, there may also be mentioned synthetic resin combinations based on acrylate resin, unsaturated monomers reacting therewith, and a peroxide catalyst.

In order to achieve a uniformly distributed conductivity over the entire surface of the coating, the mixture according to the invention contains an anti-sedimentation agent, which prevents sedimentation of the aluminium grit particles away from the surface of the floor covering, which is liquid during application. Without this, after curing, the surface layer which has become enriched in binder would exhibit an excessive electrical resistance. As anti-sedimentation agents it is in principle possible to use thixotropic agents, such as, for example, silicon dioxide ("Aerosil") and montmorillonite ("Bentones"). The use of finely dispersed asbestos, such as, for example, "Sylodex" (of Messrs. Grace Co.), offers the advantage that it need not be dispersed separately but can be dispersed directly together with aluminium grit in the resin, using simple mixing machines, and exhibits a good anti-sedimentation action and good levelling properties.

The mixing according to the invention can be manufactured according to conventional methods. Preferably, various colour pastes, which consist of approx. 50% of pigment -- it being possible to use all known inorganic and numerous organic pigments -- and approx. 50% of resin, are manufactured by grinding on triple-roll mills or dispersing in Cowles dissolvers. These colour pastes are then introduced into a mixing vessel, after which the remainder of the resin is stirred in. Thereafter, the anti-sedimentation agent can be dispersed in the mixture and finally the aluminium grit, preferably of 99.5-99.7% purity and of 0.35-1.2 mm particle size, and, optionally, the additives required to achieve additional properties, such as levelling agents and de-aerating agents, can be stirred in. Separately from this basic mixture, which in commercial products is frequently also referred to as component I, the curing agent, or component II, is supplied in amounts corresponding to the mixing ratio required for optimum curing.

Before use, the two components are thoroughly mixed together, poured out into the surface to be treated and spread uniformly, by means of a serrated trowel, to give a coating of the desired thickness, which can be between 3 and 5 mm. During the process, care must be taken that the aluminium grit is not distributed unevenly by the movement of the serrated trowel, because of the relatively large particle size of the grit. To achieve optimum levelling of the slightly thixotropic liquid mass, a subsequent treatment with a plastic spiked roller is carried out, which permits de-aeration and achieves bubble-free surfaces.

In order to achieve better de-aeration of the liquid mass during laying, and bubble-free surfaces of the coverings, it is possible to add 1-5%, preferably 1.5-2%, of paraffin oil or benzine (boiling range 100°-125° C) into the mixture which has been prepared for laying.

If, as is usually the case, the floor to be laid has a leakage resistance of 10² -10⁴ ohm, it easily proves possible, using the mixture according to the invention, to manufacture coverings which exhibit the leakage resistance of less than 10⁶ ohm required by the DIN specification. In most cases, coverings with a leakage resistance of 10³ ohm or less are obtained. If the bases to be covered have higher leakage resistances than 10⁴ ohm, it is necessary to provide earthed underlays in the form of metal fabrics, metal foils or metal grids.

The coverings described in the examples which follow can readily be cared for by simple cleansing agents, show no conspicuous wear after months of exposure to chemicals, and to the customary traffic in manufacturing areas of chemical concerns, and retain their initial value of the leakage resistance.

EXAMPLES 1 - 6

In the examples which follow, the components mentioned are mixed with one another.

    ______________________________________                                         1.  Epoxide resin based on the glycidyl ether of                                   4,4'-dihydroxydiphenylmethane, diluted with                                    25% of cresyl glycidyl ether (viscosity at                                     25° C: 500-700 cP, epoxide equivalent weight                            185-192)                   303     g                                           Chrome oxide green         20      g                                           Titanium dioxide           8       g                                           Thixotropic agent based on asbestos (for ex-                                   ample "Sylodex" of Grace Co.)                                                                             3       g                                           Aluminum grit (0.35-1.2 mm)                                                                               573     g                                           Curing agent based on an adduct of trimethyl-                                  hexamethylenediamine and a liquid epoxide resin                                based on bisphenol-A       56      g                                           3-Aminomethyl-3,5,5-trimethyl-cyclohexylamine                                                             37      g                                           Total                      1,000   g                                       ______________________________________                                         ______________________________________                                         2.  Epoxide resin as in Example 1                                                                             293     g                                           Phthalocyanine blue        0.5     g                                           Titanium dioxide           19.5    g                                           Thixotropic agent based on asbestos                                                                       4.0     g                                           Aluminum grit (0.35-1.2 mm)                                                                               560     g                                           Liquid polyaminoamide resin (viscosity 869 cP,                                 amine content 13.62%, mol/kg 9.5)                                                                         103     g                                           Paraffin oil               20      g                                           Total                      1,000   g                                       ______________________________________                                    

    ______________________________________                                         3.  Epoxide resin based on an                                                      addition product of penta-                                                     erythritol glycidyl ether and bisphenol-A                                      (viscosity at 25° C: 1,300-1,800 cP, epoxide                            equivalent weight: 148-158)                                                                               273.5   g                                           Titanium dioxide           22.0    g                                           Hydrated chrome oxide green                                                                               5.5     g                                           Thixotropic agent based on asbestos                                                                       3.0     g                                           Aluminum grit (0.35-1.2 mm)                                                                               571.0   g                                           Paraffin oil               16.0    g                                           Curing agent based on an adduct of trimethyl-                                  hexamethylenediamine and a liquid epoxide resin                                based on bisphenol-A       22.0    g                                           Bis-(3-methyl-4-amino-cyclohexyl)-methane                                                                 87.0    g                                           Total                      1,000.0 g                                       ______________________________________                                    

    ______________________________________                                         4.  Epoxide resin based on the glycidyl ether of                                   4,4'-dihydroxydiphenylmethane (viscosity                                       12,000-                                                                        16,000 cP, epoxide equivalent weight                                           185-210)                   225.0   g                                           Pentaerythritol glycidyl ether                                                                            25.0    g                                           Titanium dioxide           21.0    g                                           Yellow iron oxide          9.0     g                                           Thixotropic agent based on asbestos                                                                       4.0     g                                           Aluminum grit (0.35-1.2 mm)                                                                               571.0   g                                           Benzine (boiling range 100-125° C)                                                                 20.0    g                                           Curing agent based on a trimethylhexa-                                         methylene-                                                                     diamine adduct and a liquid epoxide resin                                      based on bisphenol-A       26.0    g                                           3-Aminomethyl-3,5,5-trimethylcyclohexylamine                                                              73.0    g                                           Benzyl alcohol             26.0    g                                           Total                      1,000.0 g                                       ______________________________________                                         ______________________________________                                         5.  Branched polyalcohol with ether and ester                                      groups, having a viscosity of 5,000 cP at                                      20° C,                                                                  hydroxyl content approx. 5%, acid number                                       <2 and water content 0.2%  167.0   g                                           Ether-alcohol (viscosity 34 cP at 20° C,                                hydroxyl                                                                       content approx. 11%, water content <0.1%)                                                                 11.0    g                                           50% strength colour paste of the above resin                                   and                                                                            titanium dioxide/chrome oxide green 1:1 parts                                  by weight                  116.0   g                                           Molecular sieve paste (for example Zeolite L-                                  paste)                     61.0    g                                           Thixotropic agent based on asbestos                                                                       7.0     g                                           Aluminum grit (0.35-1.2 mm)                                                                               536.0   g                                           Curing agent based on 4,4'-diphenyl-                                           methanedi-                                                                     isocyanate, viscosity 130-155 cP at 25° C,                              isocyanate group content approx. 30%)                                                                     102.0   g                                           Total                      1,000.0 g                                       ______________________________________                                         ______________________________________                                         6.  Unsaturated, liquid polyester resin with                                       styrene                                                                        as the reactant (viscosity approx. 5,300 cP                                    at 25° C)           352.0   g                                           1% strength cobalt octoate 2.5     g                                           50% strength colour paste of the above resin                                   and                        and                                                 titanium dioxide/chrome oxide green, 2:3                                                                  61.0    g                                           Thixotropic agent based on asbestos                                                                       3.0     g                                           Aluminium grit (0.35-1.2 mm)                                                                              555.0   g                                           Paraffin oil               19.0    g                                           Catalyst consisting of a 50% strength solu-                                    tion of methyl ethyl ketone peroxide in the                                    plasticiser                7.5     g                                           Total                      1,000.0 g                                       ______________________________________                                         __________________________________________________________________________     Properties of the floor coverings manufactured with the mixtures from          Examples 1-6                                                                   __________________________________________________________________________                        1     2    3     4     5           6                        __________________________________________________________________________     Colour shade of the covering                                                                      green blue light yellow                                                                               light       light                                                  green       green       green                    Degree of filling resin/curing                                                                    1:1.52                                                                               1:1.47                                                                              1:1.57                                                                               1:1.6 1:1.7       1:1.4                    agent: filler                                                                  Working time at 20° C/l kg                                                                 approx.                                                                              approx.                                                                             approx.                                                                              approx.                                                                              approx.     approx.                                     11/2 hrs.                                                                            2 hrs.                                                                              23/4 hrs.                                                                            11/2 hrs.                                                                            3/4 hr.     3/4 hr.                  Leakage resistance in ohm                                                                         <10.sup.3                                                                            <10.sup.3                                                                           <10.sup.3                                                                            <10.sup.3                                                                            <10.sup.3   <10.sup.3                according to DIN 51,953                                                        Compressive strength (DIN                 The cured                            53,454) in kp/cm.sup.2                    covering is                          after 1 week       672   556  576   432   too elastic 637                      after 4 weeks      699   595  725   585   and too soft                                                                               760                                                                for measur-                          Flexural strength (VSM 77,103)            ing the                              in kp/cm.sup.2 after 1 week                                                                       305   510  497   322   mechanical  461                      after 4 weeks      290   192  498   295   strengths   501                      Impact strength (VSM 77,105)                                                   in kp.cm/cm.sup.2 after 1 week                                                                    1.22  3.46 5.13  3.77              2.72                     after 4 weeks      1.29  2.82 4.68  3.53              2.82                     Modulus of elasticity (DIN                                                     53,457) in kp/mm.sup.2                                                         after 1 week       376   352  397   284               404                      after 4 weeks      404   376  423   306               369                      Special properties resistant                                                                            as in                                                                               high re-                                                                             easy  very elastic,                                                                              high                                        to water,                                                                            Example                                                                             sistance                                                                             process-                                                                             rubbery,    com-                                        dilute                                                                               1    to agg-                                                                              ability,                                                                             sound-      pressive                                    inorganic  ressive                                                                              attrac-                                                                              absorbing   strength                                    acids and  organic                                                                              tive                                                          bases and  solvents,                                                                            level-                                                        benzine    high com-                                                                            ling,                                                                    pressive                                                                             good                                                                     strength,                                                                            stability                                                                good sta-                                                                            of colour                                                                bility of                                                                            shade                                                                    colour                                                                         shade                                            __________________________________________________________________________

EXAMPLE 7

The following components are mixed with one another:

    ______________________________________                                         Epoxide resin based on the glycidyl ether of                                   4,4'-dihydroxydiphenylmethane (viscosity 8,000-                                12,000 cP at 25° C. epoxide equivalent weight                           187-196)                  238.0    g                                           Hexanetriol triglycidyl ether (viscosity 115 cp                                at 25° C, epoxide equivalent weight 140-150)                                                      21.5     g                                           1,4-Butanediol diglycidyl ether (viscosity 14-22 cP                            at 25° C, epoxide equivalent weight 125-143)                                                      1.5      g                                           Titanium dioxide          8.0      g                                           Chrome oxide green        4.5      g                                           Thixotropic agent based on montmorillonite (for                                example "Bentone 27" of National Lead Co.)                                                               11.0     g                                           Aluminum grit (0.35-1.2 mm)                                                                              550.0    g                                           Curing agent based on an adduct of trimethyl-                                  hexa-                                                                          methylenediamine and a liquid epoxide resin                                    based on bisphenol-A      32.0     g                                           3-Aminomethyl-3,5,5-trimethylcyclohexylamine                                                             56.0     g                                           Benzyl alcohol            62.0     g                                           Paraffin oil              15.5     g                                            Total                    1,000.0  g                                           ______________________________________                                    

A floor covering is produced with this mixture.

    ______________________________________                                         Colour shade of the covering                                                                             green                                                Degree of filling, resin/curing agent:filler                                                             1:1.35                                               Working time at 20° C/l kg                                                                        about 1 hour                                         Leakage resistance in ohm according to DIN                                     51,953                    10.sup.3                                             ______________________________________                                     

What we claim is:
 1. A mixture for the manufacture of antistatic floor coverings or coatings which comprises, based on the total mixture, 30 to 45% by weight of a cold-curing liquid epoxy resin combination; 45 to 70% by weight of aluminum grit the particles of which have a length of 0.35 to 1.2 mm; 0 to 30% by weight of a pigment; and 0.3 to 1.1% by weight of a thixotropic agent.
 2. A mixture according to claim 1, characterised in that it contains 30-45 percent by weight of a resin combination, 3-30 percent by weight of pigment and 45-65 percent by weight of aluminium grit.
 3. A mixture according to claim 1, characterised in that it contains, as the synthetic resin combination, an epoxide resin and a curing agent for epoxide resins.
 4. A mixture according to claim 1, characterised in that it contains an epoxide resin based on aromatic compounds.
 5. A mixture according to claim 4, characterised in that it additionally contains an aliphatic epoxide resin.
 6. A mixture according to claim 3, characterised in that it contains liquid, aliphatic or cycloaliphatic, polyamines, or their liquid adducts, containing at least one primary amino group, with polyepoxides, as curing agents.
 7. A mixture according to claim 3, characterised in that it contains liquid polyaminoamide resins as curing agents.
 8. A mixture according to claim 1, characterised in that it contains 1-5 percent by weight of paraffin oil or benzine.
 9. A mixture according to claim 1, characterised in that it contains, as a thixotropic agent, silicon dioxide, montmorillonite or finely divided asbestos.
 10. A mixture according to claim 1, characterised in that it contains 50-60 percent by weight of aluminium grit. 